Off-plane technique ultrasound-guided pericardiocentesis via anterior approach: short communication

The pericardiocentesis procedure is common, often performed via the subxiphoid approach, although other transthoracic approaches have been described. This short communication describes an off-plane technique ultrasound-guided pericardiocentesis using an anterior approach, performed using a linear transducer and guided in real-time by ultrasound, offering the advantage of continuous needle tracking to reduce complications associated with this approach such as pneumothorax, inadvertent cardiac puncture, and injury to the left internal mammary artery (LIMA).


Introduction
The pericardium is a relatively rigid sac that envelops the heart and the roots of the great vessels, working as a point of fixation and physical barrier for the heart [1].It consists of two layers: a parietal layer, which is fibrous, and a visceral layer, which is a serous membrane.The space between these two layers is known as the intrapericardial space, which contains about 20-25 ml under normal conditions [2].Pericardial effusion is defined as the abnormal accumulation of fluid in the pericardial cavity, which can develop due to overproduction of pericardial fluid, decreased reabsorption, or an imbalance between approaches for performing this procedure.Therefore, ultrasound-guided pericardiocentesis should be considered the "gold standard" in contemporary practice [9].
The subxiphoid approach is the most employed technique; however, during this procedure, it is difficult to guide the puncture in real time due to the anatomy and position of the needle.Ultrasound ends up being more of a tool for confirming intrapericardial position rather than real-time guidance [2].Approaches for pericardiocentesis via anterior, subcostal in-plane [6], and anterior in-plane routes have been described [10].In this study, we aim to describe an anterior off-plane technique that allows for continuous evaluation of the pleura and the anatomical location of the left internal mammary artery (LIMA) to avoid pneumothorax and inadvertent puncture of the LIMA.

Technique
This technique is demonstrated in a 63-year-old patient with a history of breast cancer who presents with symptoms of dyspnea and cough, and echocardiography reveals signs of cardiac tamponade secondary to malignant pericardial effusion.
Pericardiocentesis via anterior off-plane approach guided by real-time echocardiography is described as follows, a SonoSite M-Turbo ultra-sound machine with a 5-MHz small-footprint convex transducer and a 13-MHz linear transducer were used.
1.The pericardiocentesis kit is prepared, it contains a 16-gauge thoracentesis needle, an 8.5 Fr dilator, an 8.0 Fr catheter, and a metal guide (Fig. 1a).2. The patient is placed in the supine position with the head elevated between 30 and 40 degrees.3. Echocardiographic assessment is performed at the patient's bedside using the four basic windows: long axis, short axis, apical four-chamber, and subxiphoid views.The most important window in this procedure is the long-axis view, where the pericardial effusion should be anterior (between the thoracic wall and the right cavities) (Fig. 1b), if there is not anterior pericardial effusion, this technique is contraindicated; also it is recommended to assess hemodynamic repercussion by evaluating transmitral variability (Fig. 1c).4. If fluid is observed in the anterior space with a low frequency convex transducer, its distance between the thoracic wall and the pericardium should be measured with a high frequency linear transducer, to consider anterior approach it should be greater than 15 mm in diastole.The 4th and 6th intercostal spaces should also be evaluated, and the widest space should be selected (Fig. 2c and d). 5.It must be ensured that the LIMA is not in the puncture trajectory.The LIMA has been described to be laterally around 1.47 +/-0.30cm from the sternum [11] (Fig. 2a) and it is recommended whenever possible to visualize the LIMA prior to needle entry for a safer puncture [12,13]; in our experience, Doppler assessment is not always able to clearly show its location.Therefore, for this technique, it is suggested that the transducer be placed longitudinally parallel to the sternum as close as possible and not beyond 1 cm of it (Fig. 2c).Doppler color should also be used to rule out the presence of any vessel in the puncture trajectory.6.After asepsis and antisepsis, with the linear transducer in longitudinal plane (Fig. 2b, c and d), the puncture is made off-plane and guided in realtime until its entry into the pericardium (Fig. 3a and  b).The puncture is performed at the center of the transducer with minimal inclination to allow the visualization of the needle throughout the trajectory until reaching the pericardium (Fig. 3a).It has been described that a greater angle of needle entry results in less pronounced scattering artifact; however, the needle tip may appear less visible when entering the pericardium, potentially causing inadvertent puncture of the heart due to this effect [14].To prevent inadvertent punctures, we recommend maintaining negative pressure with the syringe once the skin is pierced and stopping the advancement of the needle once fluid return is obtained.Additionally, it is important to measure the thickness of the thoracic wall to have a preliminary idea of the distance the needle needs to be inserted prior to the puncture.7. Once the needle is positioned (Fig. 3b), the metal guide is passed, and its entry into the pericardium is verified (Fig. 3c).It is recommended to insert the guide 5-7 cm, depending on the thoracic thickness.8. Once it is confirmed that the guide is in the pericardium, an 8.5 Fr dilator is inserted 1-3 cm, depending on the thoracic thickness (Fig. 3d).9.The dilator is removed, and an 8 Fr pigtail catheter is inserted up to 10 cm, ensuring that no hole remains outside the thorax.Return is verified, and it is connected to a drainage bag or a Pleur-Evac drainage system (Fig. 4a and b).
10.If samples are required, it is recommended to connect to a three-way stopcock to have a route for sample collection, while the drainage is left in place.11.It is recommended to secure with 2 − 0 silk (Fig. 4c).12. Once at least 200 cc have been drained, a new echocardiographic evaluation is recommended, observing a decrease in effusion (Fig. 5a) and evaluating transmitral flow to assess changes in hemodynamic repercussion (Fig. 5b).13.Finally, the absence of pneumothorax should also be evaluated by assessing pleural sliding and the presence of the seashore sign in the nearest pleural space that can be visualized (Fig. 5c).14.In this patient, pericardial thickening suggestive of neoplastic etiology of the effusion is observed, so a chest tomography is performed to show how close the distance is between the catheter passage and the LIMA (Fig. 6).
This technique is similar to that described by Osman et al. [7] for sternal in-plane pericardiocentesis.Osman recommends a needle entry inclination of 45 degrees for visualization throughout its trajectory; however, if the Our research group previously presented a series of ultrasound-guided thoracentesis performed off-plane, where the complication rate was 1.2%, with no vascular injury complications [15].It is clarified that the use of off-plane techniques requires excellent hand control and probe-needle coordination, especially with very long pericardiocentesis needles.Therefore, it is recommended that this procedure be performed by personnel experienced in ultrasound-guided procedures.

Conclusion
The off-plane anterior pericardiocentesis approach offers the advantage of never losing sight of the needle tip, unlike other approaches, especially the subxiphoid approach, where observing needle entry into the pericardium in obese patients is highly challenging.This enables us to minimize the risk of pneumothorax, inadvertent cardiac puncture, and injury to the LIMA.

Fig. 3 Fig. 2
Fig. 3 (a) Diagram of the puncture technique, it must be performed at the center of the transducer with minimal inclination (green angle) to allow the visualization of the needle throughout the trajectory.LIMA: Left internal mammary artery.(b) The puncture is made off-plane and guided in real-time until its entry into the pericardium (c) The metal guide is passed to the pericardium and verified in real time (d) 8.5Fr dilatator is inserted 1-3 cm

Fig. 6
Fig. 6 CT scan showing distance between the catheter passage and the LIMA.CT: computed tomography, LIMA: left internal mammary artery